Adding self-x capabilities to AMR sensors as a first step towards dependable embedded systems

Embedded systems exist in every modern device. More applications and functionalities increase the complexity of products. With the introduction of cyber-physical system (CPS), more interaction between physical input and output increases the needs for dependable systems. Sensors are not only adding to the intelligence level of the system but are also one of the sources of deviations in measurement. The main challenge now is to increase the robustness of the sensor itself. In this paper an anistropic magnetoresistance sensor or AMR sensor has been chosen as a case study for self-x feature implementation, because it provides integrated actuator together with the sensor. This sensor has a degradation problem towards changes of temperature. Most of the available solutions, if they take this problem into account at all, now require additional temperature sensors in order to correct the error. These solutions increase the costs and consume space in embedded systems. A new solution with minimum costs, minimum number of components and higher accuracy is required. As magnetic sensors are widely used for electronic compasses in mobile devices, with volumes of several millions every year, even small cost reductions will be significant. In this paper, a method for temperature measurement in AMR sensors has been developed, modeled and verified by experiments to use the sensor bridge itself as an implicit temperature sensor.